No matter how much screening you do or rules you have in the rental agreement, your tenants can be a contributing factor.I'd rather improve a neighborhood with involved citizens, grant money, the support of the city, and relationships with other landlords than have it legislated.

Knock on doors, call owners directly, look for signs of distress, etc).

So far all that we have tried is the regular Allure, which has been good so far, but I would not be surprised if there is some peeling with water at some point- especially in bathrooms or basements.

Loud, vicious barking dogs next door to the subject property.  

I don't think that I would want to live next door to my business partner if things got bad.  

No matter what you do or try to do, you will never be able to improve your neighbor's property.  

Any concerns about putting wood in a bathroom?

Very nice, the bathroom tile looks great!

I don't know your background, but I'm going to assume you haven't managed this many doors before, and you probably have a day job.  

It said that the single best ROI would come from a fresh coat of paint on the front door.